1. Field of the Invention
The present invention relates to a multi-strobe generation apparatus for generating a multi-strobe having a plurality of strobes, a test apparatus for testing electronic devices and an adjustment method for adjusting timing for generating each strobe of the multi-strobe. Specifically, the invention relates to a multi-strobe generation apparatus for controlling the timing for generating the respective strobes.
2. Description of Related Art
Conventionally, a change point or the like of value of a signal to be measured is detected by outputting one strobe while delaying per cycle of the signal to be measured and by detecting the value of the signal to be measured in each strobe. This method is used to detect a change point or the like of value of a data signal and a DQS signal in a setup/hold test or the like of a memory for example.
A double data rate type device such as a DDR-SDRAM (Double Data Rate-SDRAM) that outputs a data signal in synchronism with a leading or trailing edge of a clock (DQS) outputs clock following to the data signal per predetermined output data width. Thereby, the setup/hold timing condition in passing data is relaxed. Such a device is required to have a predetermined setup time and hold time between the data signal and the clock in order to set up/hold the data without error.
Conventionally, the value of the data signal and the value of the clock are detected by one strobe, respectively, to detect change points of the respective values. Then, it is judged pass/fail of the tested device by judging whether or not the respective change points thus detected satisfy the predetermined setup time and hold time.
However, because the values are detected per each cycle of the data signal and DQS by one strobe, it is unable to test accurately when jitter occurs in the data signal and DQS due to various factors such as fluctuation of power and thermal fluctuation of the device. Still more, it takes time for the test because the data signal and DQS are scanned by one strobe.